Why are the streets so clean?

The street sweeper just went by, as usual on a Friday morning. Every Friday, like clockwork. I used to think this was odd. Not that they clean the streets, but that it is done so frequently. I thought with most cities struggling with reduced budgets, they're always looking for something to cut, and street sweeping seemed a likely candidate. But I found out that because the storm drains flow directly into the Bay, they're concerned about debris getting washed into the drains, polluting the Bay and endangering the marine life. So there you have it.